Michel de La Force, chairman of the General Confederation of Managers, has said that "digital working time" would have to be measured. Some emailing outside of office hours would be allowed but only in "exceptional circumstances".

France has a 35-hour week, adopted in 1998. But the French are not alone in worrying about how portable devices have exposed employees to longer hours.

In the UK there is protection for many types of worker in the form of the Working Time Regulations, but the TUC argues this simply doesn't cover out-of-hours email. And there are exemptions for categories of worker like lawyers and doctors.

UK working hours

Employers can't force adults to work more than 48 hours a week - normally averaged over 17 weeks.

Exceptions apply:

Where the working time is not measured and the worker is in control - eg managing executives

In the armed forces, emergency services and police - in some circumstances

In security and surveillance

As a domestic servant in a private household

Where 24-hour staffing is required

Certain categories of seafarers, sea-fishermen and workers on vessels on inland waterways

If an out-of-hours email ban was brought in, the situation could be similar and not everybody would be protected, says Andrew Lilley, an employment lawyer and managing partner at law firm Travers Smith. "I imagine many jobs would be exempt, a bit like some of the exemptions in the Working Time Regulations."

Disruptive email is mainly a white-collar problem. It goes with the territory for certain jobs, such as lawyer or financier, where staff are managing their own time. But others further down the hierarchy working on fixed hours contracts are perhaps also in need of protection.

Technology has redrawn the working day. Woody Allen's 1972 film Play It Again Sam contains a running gag about a workaholic businessman. Played by Tony Roberts he begins every scene by phoning the office to give the telephone number where he can be reached and for how long, followed by the next contact number. He was the exception - workers used to be able to disappear. Today anyone with a smartphone is usually reachable.

Open all hours in the US

An advertising professional who moved from London to New York describes a different email culture.

"I remember on my second day seeing an email from a work colleague sent very late that evening. To my surprise someone replied to it, and then the interaction continued online. And lo and behold we 'were working'. By contrast, in the UK, if I worked late I would often draft emails but save them in my inbox and send them first thing the next morning. That now seems ridiculous and archaic to me. Emails are constant here. It's not that they expect you to answer out of office hours. More that everyone is 'switched on' all the time - that's the culture and pace of New York. I never really heard the concept of work/life balance when I got to the US. There wasn't much complaining as people's expectations were different. It's not just in the corporate world. When my family were moving here and trying to get an apartment I remember being surprised and delighted that our realtor was calling and emailing us late on a Saturday night."

Michael Reid, an IT teacher at a Liverpool comprehensive, says his evenings are regularly interrupted. "An email arrives at 11.45pm and you know a colleague is working late and you want to support them." When he sees it in his inbox he is "crestfallen", he says. "It takes the joy out of what you are doing."

An advertising consultant in London, who wants to remain anonymous, says she is expected to respond to emails. Many come through between 18:00 and 22:00. "Needless to say not all emails require an immediate response though if I'm to tell which do and don't, I do need to check them." Requests for information she accepts as part of the job. Others - "can I remind you of X" or invitations to meetings with no context - drive her "nuts", she says. She now switches her phone off when she goes to bed to ensure an uninterrupted night's sleep.

Enforcing an email ban would be almost impossible, argues Alief Rezza, an oil analyst in Stavanger, Norway. He checks email every half hour when he leaves work at 16:30 until 19:00. The stock market is still open and he might get an urgent message from colleagues in London. When he wakes he checks to see if colleagues in the US or Singapore have been in touch. "I don't think a ban would work. If Norway bans my company from sending emails to me then my company needs to make sure someone is able to cover the request that should have been in my inbox." The industry would find a way around it, he argues.

Like many other lawyers, Lilley checks work email every hour or so during the evening and the same on holiday. In the days before smartphones he would receive phone calls. An email is less intrusive, he argues. "The ability to be contactable on email means that a lot of people leave the office earlier than otherwise would be the case." It can be inconvenient of course. "You can't deny there are occasions where you think I'd prefer to finish what I'm doing. I've had to stop working out in the gym to reply to a work email." But if you want to do a certain kind of legal work you have to be willing to be interrupted, he argues. And there is reassurance in knowing that colleagues can get hold of you to check crucial details.

More from the Magazine

In the office we shop, email friends and go to the gym - the only thing we don't do much of is work. Meanwhile, at home we do our work email, take part in conference calls, write reports and have our best ideas, says Lucy Kellaway.

Paul Sellers, TUC policy adviser, says the same problem that France is seeking to address exists in the UK. He says people in the law, media, finance and local government are not being allowed to switch off. "Why are we expecting people to work at 8.30 at night?" The Working Time Regulations were drawn up in the 1990s before mobile phones were in wide circulation. The rules have not caught up.

NHS workers are paid to be on call even if they end up not working. "If you're not being paid you're not being valued," Sellers says.

A ban on email is not the answer, argues Ksenia Zheltoukhova, research associate at the Chartered Institute of Personnel and Development. It could even hurt workers who increasingly require flexible working - keeping in touch on trains, emailing between time zones and leaving early to look after the children. A better approach is to educate managers about work-life balance and encourage them to prioritise.

For some employees, the problem is not the email itself, but the collateral damage to loved ones. "For me out of hours emails go with the territory," says the advertising consultant. "But my partner does mind." Lilley once thought he'd perfected the discreet glance at the phone during dinner. Now he's not so sure. "I suspect you're more distracted in company than you think you are. It can be very irritating to people around you."